My sister told me to read _Goblin Quest_, and while it doesn't count as a good book for the purposes of this thread I feel it deserves a mention. It's about a goblin who gets shanghaied by a group of adventurers. It is very D&D.

The goblin notices that in the fight where all his goblin compatriots were killed, the wizard didn't cast any spells. Instead, he stayed back shooting arrows to save his spells for later.